If you're having trouble finding a full-on catamaran trailer you could buy a standard utility trailer and then weld some crossbars and a mast support onto it. Just a thought.

Right now I have rollers at all four corners; but I need a new front crossbar (my current one is bending slightly) and I think I'll build hull cradles for the front. Spread out the weight some on the hull.

I had to fabricate/modify my trailer.
A lesson that was tought to me by the school of hard knocks was, make sure the wheels are between the hulls.

My error was to buy a trailer that had the same distance beteen the wheels as between the centerlines of the hulls. Now my boat sits real high off the ground so it will clear the wheels. It's not a real heavy boat so it's not to hard to get up there but its harder than has to be.

For rollers I used just a two ten inch rollers and four eight inch guide rollers down the legenth of either hull on the inside to make it as narrow as possable. The boat is not resting on rollers. Rather on planks two 2"x15'. This way boats weight is distributed more evenly and I won't get alot of small soft spots down the legenth of the hulls from spending long winters on rollers. To secure the boat I used four wratchet straps and eye bolts. Each set pulling away from eachother.like so.
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The plus side to having the boat so high is that a huge litterbox easly fits under the boat to store all my hobie related gear. It's very self contained. Louvers of some sort let things moderately dry while in the box.

Oh make sure your mast rest holds the mast about 10" to 12" above your vehicle to account for changes in pitch of the road, relitave to the angle of your trailer while your vehicle is going up or down a small hill/ramp/driveway ect. Otherwise your vehicle could get dammaged.

Another lesson compliments of the school of hard knocks. Well at least my next trailer will be dead on perfect. If you have to fabricate/ modify, yours too.

Jaime,
why rollers on all four corners? Do you roll your cat up one end and down another? Do you not have planks down the legnth of your hulls? Or do you only have the crossmembers?